Exhibit 4.1


THIS DEBENTURE HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT
OF 1933, AS AMENDED (THE "SECURITIES ACT") OR ANY APPLICABLE
STATE SECURITIES LAW AND MAY NOT BE TRANSFERRED UNLESS (i) THERE
IS AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT
OR SUCH APPLICABLE STATE SECURITIES LAWS, OR (ii) IN THE OPINION
OF COUNSEL REASONABLY ACCEPTABLE TO THE COMPANY REGISTRATION
UNDER THE SECURITIES ACT OR SUCH APPLICABLE STATE SECURITIES LAWS
IS NOT REQUIRED IN CONNECTION WITH SUCH TRANSFER.

THE INDEBTEDNESS EVIDENCED BY THIS DEBENTURE IS SUBORDINATED TO
THE PRIOR PAYMENT IN FULL OF THE BANK DEBT (AS DEFINED IN THE
SUBORDINATION AGREEMENT REFERRED TO BELOW) PURSUANT TO, AND TO
THE EXTENT PROVIDED IN, THAT CERTAIN SUBORDINATION AGREEMENT
DATED MARCH 27, 1997, AMONG ENVIRONMENTAL TECTONICS CORPORATION,
SIRROM CAPITAL CORPORATION, AND FIRST UNION NATIONAL BANK.

               Environmental Tectonics Corporation

         12% Subordinated Debenture Due March 27,  2004


No. R-1                                           March 27, 1997
$4,000,000.00  

          For value received, Environmental Tectonics
Corporation, a Pennsylvania corporation (the "Company"), hereby
promises to pay to Sirrom Capital Corporation at Tandem Capital,
Inc., 500 Church Street, Suite 200, Nashville, Tennessee 37219,
or registered assigns, on the 27th day of March, 2004, the
principal amount of $4,000,000.00 and to pay interest (computed
on the basis of a 360-day year of twelve 30-day months) on the
principal amount from time to time remaining unpaid hereon at the
rate of 12% per annum from the date hereof until maturity,
payable quarterly on the first day of each February, May, August,
and November in each year commencing May 1, 1997, and at
maturity.  The Company agrees to pay interest (computed on the
same basis) on overdue principal and premium, if any, and (to the
extent legally enforceable) on any overdue installment of
interest, at the rate of 13% per annum (or, in each case, at the
highest rate permitted by applicable law, whichever is less)
until paid.  

          Both the principal hereof and interest hereon are
payable to the order of the holder hereof at its address
registered on the books of the Company or by federal funds wire
transfer to a bank account designated in writing by the holder to
the Company in coin or currency of the United States of America
which at the time of payment shall be legal tender for the
payment of public and private debts.  If any amount of principal,
premium, if any, or interest on or in respect of this Debenture
becomes due and payable on any date which is not a Business Day,
such amount shall be payable on the next preceding Business Day. 
"Business Day" means any day other than a Saturday, Sunday,
statutory holiday or other day on which banks in Tennessee are
required by law to close or are customarily closed.

          This Debenture is one of the 12% Subordinated
Debentures due March 27, 2004 of the Company in the aggregate
principal amount of $4,000,000.00 issued under and pursuant to
the terms and provisions of the Debenture Purchase Agreement,
dated as of March 27, 1997 (the "Debenture Agreement"), entered
into by the Company with the original purchaser referred to
therein, and this Debenture and the holder hereof are entitled,
equally and ratably with the holders of all other Debentures
outstanding under the Debenture Agreement, to all the benefits
and security provided for thereby or referred to therein, and to
which Debenture Agreement reference is hereby made for all such
terms and provisions.

          This Debenture is subordinated to certain other
indebtedness of the Company to the extent and with the effect set
forth in the Subordination Agreement between the Company, First
Union National Bank, and Sirrom Capital Corporation dated as of
March 27, 1997.

          If an Event of Default, as defined in the Debenture
Agreement, occurs and is continuing, the principal of this
Debenture and the other Debentures outstanding under the
Debenture Agreement may be declared due and payable in the manner
and with the effect provided in the Debenture Agreement.

          This Debenture is registered on the books of the
Company and is transferable only by surrender thereof at the
principal office of the Company at 125 James Way, Southampton,
Pennsylvania 18966-3877, or such other address as the Company
shall have advised the holders of the Debenture in writing, duly
endorsed or accompanied by a written instrument of transfer duly
executed by the registered holder of this Debenture or its
attorney duly authorized in writing.  Payment of or on account of
principal, premium, if any, and interest on this Debenture shall
be made only to or upon the order in writing of the registered
holder.

          If the indebtedness represented by this Debenture or
any part thereof is placed in the hands of attorneys for
collection after an Event of Default, or the enforcement of any
rights under the Debenture Agreement, the Company agrees to pay
the principal, premium if any, and interest due and payable
hereon, and an amount equal to all costs of collecting this
Debenture, including reasonable attorneys' fees and expenses.

          This Debenture and the Debenture Agreement are governed
by and construed in accordance with the laws of the State of
Tennessee.     


[Corporate Seal]              ENVIRONMENTAL TECTONICS CORPORATION

                              By/s/ Duane Deaner                 
                                        Duane Deaner, Chief
                                        Financial Officer

                              ATTEST:/s/ Richard E. McAdams      

                                        Secretary